Giant leaps expected to continue in steel processing

One development that the entire iron mining industry in North America is watching closely is a plan by Indias Essar Steel Ltd. to resume iron pellet production on Minnesotas Mesabi Rangeand using the taconite pellets to make steel in Minnesota rather than shipping them to a blast furnace elsewhere.

Essar Steel, which purchased Canadas Algoma Steel Inc. for $1.6 billion in 2007, is rehabilitating a long-closed taconite processing plant near Nashwauk, Minn., with plans to make 6.5 million tons of iron pellets annually. Essar told analysts that for the foreseeable future it will ship pellets to the Essar Steel Algoma Inc. steelmaking complex near Sault Ste. Marie, Ontario, but the company hopes to begin making steel in Minnesota by 2015.

Sustainability in metals processing is all about two things: Controlling the energy inputs in processing to reduce the carbon footprint, and making end-use metals that are lighter, stronger and harder.

Richard J. Fruehan, co-director of Carnegie-Mellon Universitys Center for Iron and Steel Research in Pittsburgh, pointed out that the steel industry has made several giant leaps in processing technology. The biggest change, he said, was the adoption of continuous casting. "You saved energy with continuous casting because the ratio of steel produced to steel shipped was reduced." Continuous casting also helped eliminate primary rolling mills, thereby reducing even more energy inputs. The second most significant advancement in steel processing was the advent of thin-slab casting, Fruehan said.

Further downstream, researchers are looking at ways to harden and lighten steel. Yung C. Shin, professor of advanced manufacturing in the School of Mechanical Engineering at Purdue University in West Lafayette, Ind., is part of a team that has developed and demonstrated the capabilities of selective laser hardening of various steels. Precisely controlled laser hardening can increase the hardness of steel parts at selected areas to a theoretical maximum value. So far, the process has been shown to work well with various complex geometries, such as gears, crankshafts and splines, he said.

The process involves no induction coils or coolants, making it more environmentally benign than more traditional hardening processes. "Laser hardening is a dry process," Shin said. "In more traditional hardening, companies pay a lot of money for oil for quenching the parts. They also have to pay for the disposal of the used oil."

Other researchers are looking at innovative ways to make steel more environmentally friendly. Researchers at Worcester Polytechnic Institute in Massachusetts and the Kroll Institute for Extractive Metallurgy at the Colorado School of Mines are seeking environmentally friendly ways to reclaim spent foundry sand.

Foundries use clean, uniformly sized, high-quality silica or lake sand bonded to form molds for ferrous and nonferrous metal castings. About 1 ton of foundry sand is used in the production of each ton of iron or steel castings. Researchers estimate that 10 million to 15 million tons of foundry sand is used and discarded in the United States each year. Finding a way to recover much of that sand could eliminate the need to quarry additional quantities of new sand each year.

Have your say

All comments are subject to editorial review.
All fields are compulsory.